[PATCH 5/6] tracing: Have option files inc the trace array ref count

[Steven Rostedt <rostedt@goodmis.org>]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The option files update the options for a given trace array. For an
instance, if the file is opened and the instance is deleted, reading or
writing to the file will cause a use after free.

Up the ref count of the trace_array when an option file is opened.

Link: https://lore.kernel.org/all/1cb3aee2-19af-c472-e265-05176fe9bd84@huawei.com/

Cc: stable@vger.kernel.org
Fixes: 8530dec63e7b4 ("tracing: Add tracing_check_open_get_tr()")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b82df33d20ff..0608ad20cf30 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8988,12 +8988,33 @@ trace_options_write(struct file *filp, const char __user *ubuf, size_t cnt,
 	return cnt;
 }
 
+static int tracing_open_options(struct inode *inode, struct file *filp)
+{
+	struct trace_option_dentry *topt = inode->i_private;
+	int ret;
+
+	ret = tracing_check_open_get_tr(topt->tr);
+	if (ret)
+		return ret;
+
+	filp->private_data = inode->i_private;
+	return 0;
+}
+
+static int tracing_release_options(struct inode *inode, struct file *file)
+{
+	struct trace_option_dentry *topt = file->private_data;
+
+	trace_array_put(topt->tr);
+	return 0;
+}
 
 static const struct file_operations trace_options_fops = {
-	.open = tracing_open_generic,
+	.open = tracing_open_options,
 	.read = trace_options_read,
 	.write = trace_options_write,
 	.llseek	= generic_file_llseek,
+	.release = tracing_release_options,
 };
 
 /*
-- 
2.40.1